I tried to Google that up but got no hits. “that's him alright” - what does it mean? Is it pure slang or there is a dictionary entry explaning that?
Alright (or all right) in your sentence is used just to add emphasis:
2 used to emphasize how certain one is about something.
- "‘Are you sure it's him?’ ‘It's him all right.’"
There is no logical reason for insisting that all right should be written as two words rather than as alright, when other single-word forms such as altogether have long been accepted. Nevertheless, alright is still regarded as being unacceptable in formal writing